Selenium is an essential micronutrient for man and animals. The role of selenium has been
attributed largely to its presence in selenoproteins as the 21st amino acid, selenocysteine
(Sec, U). Sec is encoded by TGA in DNA. A unique mechanism is used to decode the UGA
codon in mRNA to co-translationally incorporate Sec into the growing polypeptide because
there is no free pool of Sec. In the human genome, 25 genes for selenoproteins have been
identified. Selenoproteins such as glutathione peroxidases, thioredoxin reductases, and …